I made some Garrett Juice concentrate up and it worked great. Now I have about a half of a gallon left. Will it keep? Should I aerate it from time to time, or all of the time? Is it OK to store it in total darkness?

If you made it yourself it will not keep. The stuff you buy at the store keeps because it has no live microbes in it.

I think it will keep for up to a week since the microbes continue to feed off the molasses. I try to make just enough for what I'll be using on the day I spray the lawn, but if I make too much, I usually find uses for it during the following week (i.e. ant mound drench or the plants that would benefit from biweekly sprayings during the growing season).

I keep mine in the garage fridge, which probably kills everything in it! I just plan on using it as a drench after that.

Patty